Use of specific copolymers for improving the cold properties of fuels or combustibles

ABSTRACT

The subject matter of the present invention is the use, for improving the cold-resistance properties of a fuel or combustible composition, of one or more copolymers comprising:—at least one unit of formula (I): in which R1 is a hydrogen atom or a methyl group; X is —O—CO—, or —CO—O— or —NH—OO— or —CO—NH—; R2 is a C6 to C24 alkyl group; and at least one unit of formula (II): in which R is a substituted or unsubstituted imidazole ring. The invention also relates to compositions of additives containing such a polymer, and also fuel or combustible compositions to which such polymers have been added, preferably in combination with a cold flow improver (CFI) additive or a paraffin anti-settling additive (WASA).

The present invention relates to the use of specific copolymers for improving the cold-resistance properties of fuels or combustibles during the storage thereof and/or the use thereof at low temperatures.

The present invention also relates to additive compositions (or “additive packages”) containing these copolymers, as well as fuel and combustible compositions to which such copolymers have been added, preferably in combination with a cold flow improver additive (CFI) and/or at least one paraffin anti-settling additive (WASA).

PRIOR ART

Fuels or combustibles containing paraffin compounds, particularly compounds containing n-alkyl, iso-alkyl or n-alkenyl groups such as paraffin waxes, are known to exhibit degraded flow properties at low temperatures, typically below 0° C. In particular, it is known that the middle distillates obtained by distillation from crude oils of petroleum origin such as diesel fuel or heating oil, contain different quantities of n-alkanes or n-paraffins depending from the source thereof. These compounds tend to crystallise at low temperatures, blocking ducts, pipes, pumps and filters, for example in motor vehicle fuel circuits. In winter or under conditions of use of fuels or combustibles at temperatures less than 0° C., the crystallisation phenomenon of these compounds can result in the reduction of the flow properties of the fuels or combustibles and hence give rise to problems during the transportation, storage and/or use thereof. The cold operability of fuels or combustibles is a very important property, particularly to ensure the cold starting of engines. If paraffins are crystallised at the bottom of the tank, they can be entrained on starting into the fuel circuit and particularly clog the filters and prefilters disposed upstream from the injection systems (pump and injectors). Similarly, for heating oil storage, if paraffins precipitate at the bottom of the tank, they can be entrained and obstruct the conduits upstream from the pump and the boiler supply system (spray nozzle and filter).

These problems are well-known in the field of fuels and combustibles, and numerous additives or additive mixtures have been proposed and marketed to reduce the size of paraffin crystals and/or change the shape thereof and/or prevent them from forming. The smallest possible crystal size is preferred as it minimises the risks of filter blocking or clogging.

Usual flow improvement agents known as cold flow improvers (CFI) are generally co- and ter-polymers of ethylene and vinyl and/or acrylic ester(s), used alone or in a mixture. These cold flow improver additives (CFI), intended to lower the cold filter plugging point (CFPP) and the pour point (PP), inhibit crystal growth at low temperatures by promoting dispersion of the paraffin crystals; these are for example polymers of ethylene and vinyl acetate and/or vinyl propionate (EVA or EVP), also commonly referred to as CFPP additives. This type of additives, very extensively known by one skilled in the art, is systematically added to conventional middle distillates at refinery outlets. These distillates containing additives are used as diesel engine fuel or as heating fuel. Additional quantities of these additives can be added to the fuels sold in service stations particularly to meet so-called Extreme Cold specifications.

To improve both the CFPP and the pour point of the distillates, it is known to add to these CFI additives, additional additives or “boosters” having the function of acting in combination with the CFI additives so as to increase the efficiency thereof. The prior art describes plenty of such additive combinations.

By way of example, mention can be made of U.S. Pat. No. 3,275,427 describing a distillation cut middle distillate between 177 and 400° C. containing an additive consisting of 90 to 10% by mass of an ethylene copolymer comprising from 10 to 30% of vinyl acetate units of weight molar mass between 1000 and 3000 g·mol⁻¹ and from 10 to 90% by mass of a lauryl polyacrylate and/or a lauryl polymethacrylate of weight molar mass ranging from 760 to 100.000 g·mol⁻¹.

Document EP0857776 proposes using alkylphenol-aldehyde resins obtained from the condensation of alkylphenol and aldehyde in association with ethylene/vinyl ester copolymers or terpolymers, for improving the fluidity of mineral oils.

Patent application WO 2008/006965 describes the use of a combination of a homopolymer obtained from an olefinic ester of carboxylic acid of 3 to 12 carbon atoms and a fatty alcohol comprising a chain of more than 16 carbon atoms and optionally an olefinic double bond and a cold flow improver additive (CFI) of EVA or EVP type, to increase the efficiency of CFI additives by amplifying the effect thereof on the CFPP.

Patent application WO 2016/128379 describes the use, as a fuel or combustible cold-resistance additive, of a block copolymer comprising:

(i) a block A consisting of a chain of structural units derived from one or more α,β-unsaturated alkyl acrylate or methacrylate monomers,

(ii) a block B consisting of a chain of structural units derived from one or more α,β-unsaturated monomers containing at least one aromatic ring.

This additive is particularly useful as a CFPP booster in association with a cold flow improver additive (CFI).

Besides improving the flow of the fuel or combustible composition, a further aim of cold-resistance additives is that of ensuring the dispersion of the paraffin crystals, so as to delay or prevent the settling of such crystals and prevent the formation of a paraffin-rich layer at the bottom of storage receptacles, tanks or containers; these paraffin-dispersing additives are known as anti-settling additives or WASA (acronym of the term “Wax Anti-Settling Additive”).

Modified alkylphenol-aldehyde resins were described in document FR2969620 as an anti-settling additive in combination with a CFPP additive.

Due to the diversification of fuel and combustible sources, there is still a need to find new additives for improving the properties of fuels or combustibles at low temperatures also known as cold-resistance properties, and particularly the flow properties thereof during the storage and/or use thereof at low temperatures.

This need is particularly important for fuels or combustibles comprising one or more paraffin compounds, for example compounds containing n-alkyl, iso-alkyl or n-alkenyl groups tending to crystallise at low temperatures.

In particular, the distillates used in fuels and combustibles are increasingly obtained from more complex refining operations than those obtained from direct petroleum distillation, and can be obtained particularly from cracking, hydrocracking, catalytic cracking processes and visbreaking processes. With the growing demand for diesel fuels, the refiner tends to introduce less readily usable cuts into these fuels, such as the heaviest cuts obtained from cracking and visbreaking methods which are rich in long-chain paraffins.

Moreover, synthetic distillates derived from the transformation of gas such as those obtained from the Fischer Tropsch process, as well as distillates resulting from the treatment of biomasses of plant or animal origin, such as in particular NexBTL and distillates comprising vegetable or animal oil esters have appeared on the market, and represent a new range of products usable as a base for formulating fuels or heating oils. These products also comprising long paraffin chain hydrocarbons.

Furthermore, the arrival of new crude oils onto the market has been observed, much richer in paraffins than those commonly refined and wherein the cold filter plugging point of the distillates obtained from direct distillation was improved with difficulty by conventional filterability additives in the same way as those cited above.

It has been observed that the cold-resistance properties of the distillates obtained by combining old bases and these novel sources were hardly improved by adding conventional filterability additives, inter alia due to the strong presence of long-chain paraffins and the complex paraffin distribution in the composition thereof. Indeed, in these novel distillate combinations, discontinuous paraffin distributions have been observed, in the presence of which known filterability additives are not always sufficiently effective.

Therefore, there is a need to adapt cold-resistance additives to these novel types of bases for fuels and combustibles, considered particularly difficult to treat.

The present invention applies to fuels and combustibles containing not only conventional distillates such as those obtained from direct crude oil distillation, but also to bases obtained from other sources, such as those described above.

Thus, the present invention aims at proposing novel additives and concentrates containing them which can advantageously be used as additives for improving the cold-resistance properties, in particular the cold flow properties of these fuels or combustibles, during the storage and/or use thereof at low temperatures, typically less than 0° C.

The present invention furthermore aims at proposing novel additives for fuels and combustibles and concentrates containing such additives, acting upon the Cold Filter Plugging Point (CFPP), the pour point (PP), and delaying and/or preventing the settling of crystals of hydrocarbon compounds, particularly paraffins.

Finally, the invention aims at proposing a fuel or combustible composition having improved cold-resistance properties, in particular at temperatures less than 0° C., preferably less than −5° C.

OBJECT OF THE INVENTION

The applicant has now discovered that specific copolymers, as described hereinafter, had unexpected properties for improving the cold resistance of fuel and combustible compositions, including those which are particularly difficult to treat.

The present invention thus relates to the use, for improving the cold-resistance properties of a fuel or combustible composition, of one or more copolymers comprising

at least one unit of the following formula (I):

wherein R₁ is a hydrogen atom or a methyl group,

X is —O—CO—, or —CO—O— or —NH—CO— or —CO—NH—, and

R₂ is a C₆ to C₂₄ alkyl group; and at least one unit of the following formula (II):

wherein R is a substituted or unsubstituted imidazole ring.

According to a preferred embodiment, the polymer defined above is used as a so-called “CFPP booster” additive, i.e. in combination with a flow improvement additive or cold flow improver additive (or CFI) wherein it improves the performances thereof.

The invention also relates to an additive composition comprising such a copolymer in association with at least one cold-resistance additive different from the copolymers according to the invention, as well as an additive concentrate containing such a composition. The cold-resistance additive is preferably selected from copolymers and terpolymers of ethylene and vinyl and/or acrylic ester(s), alone or in a mixture.

The invention also relates to a fuel or combustible composition, comprising:

(1) at least one hydrocarbon cut derived from one or more sources selected from the group consisting of mineral (preferably petroleum), animal, plant and synthetic sources, and

(2) at least one copolymer as defined above.

According to a preferred embodiment, said composition further comprises at least one cold-resistance additive different from the copolymers according to the invention defined above.

Further aims, features, aspects and advantages of the invention will emerge even more clearly on reading the description and the examples which follow.

Hereinafter, and unless specified otherwise, the bounds of a range of values are included in this range, particularly in the expressions “between” and “ranging from . . . to . . . ”.

Moreover, the expressions “at least one” and “at least” used in the present description is equivalent to the expressions “one or more” and “greater than or equal to”.

Finally, in a manner known per se, the term CN compound or group denotes a compound or a group containing N carbon atoms in the chemical structure thereof.

DETAILED DESCRIPTION

Copolymer:

The invention uses a copolymer, comprising at least one unit of the following formula (I):

wherein

R₁ is a hydrogen atom or a methyl group,

X is —O—CO—, or —CO—O— or —NH—CO— or —CO—NH—, and

R₂ is a C₆ to C₂₄ alkyl radical.

The group X of formula (I) is selected from:

X═—O—CO—, it being understood that X is then linked to the vinyl carbon by the oxygen atom;

X═—CO—O—, it being understood that X is then linked to the vinyl carbon by the carbon atom;

X═—NH—CO—, it being understood that X is then linked to the vinyl carbon by the nitrogen atom; and

X═—CO—NH—, it being understood that X is then linked to the vinyl carbon by the carbon atom.

According to a first embodiment, the group X of formula (I) is selected from: —O—CO— and —NH—CO—, it being understood that the group X═—O—CO— is linked to the vinyl carbon by the oxygen atom and that the group X═—NH—CO— is linked to the vinyl carbon by the nitrogen atom. In this embodiment, the group X of formula (I) is preferably the group —O—CO—.

According to a second embodiment, the group X of formula (I) is selected from: —CO—O— and —CO—NH—, it being understood that the group X is linked to the vinyl carbon by the carbon atom. In this embodiment, the group X of formula (I) is preferably the group —CO—O—.

According to a particularly preferred embodiment, the group X is a group —CO—O—, X being linked to the vinyl carbon by the carbon atom.

The group R₂ of formula (I) is a C₆ to C₂₄ alkyl radical. This alkyl radical can be linear or branched, cyclic or acyclic. This alkyl radical can comprise a linear or branched part and a cyclic part.

According to a first embodiment, the group R₂ of formula (I) is a linear or branched C⁶ to C₁₄, preferably C₈ to C₁₄, more preferentially C₁₂ to C₁₄ acyclic alkyl radical.

Mention can be made for example, non-restrictively, of alkyl groups such as octyl, decyl, dodecyl, ethyl-2-hexyl, isooctyl, isodecyl and isododecyl, C₁₄ alkyl groups.

According to a particularly preferred embodiment, the group X is a group —CO—O—, X being linked to the vinyl carbon by the carbon atom, and the group R₂ is a linear or branched C₈ to C₁₄, preferably Cm to C₁₄, and more preferentially C₁₂ to C₁₄ acyclic alkyl radical.

The units according to this embodiment correspond to those derived from monomers selected from alkyl acrylates and methacrylates having a C₈ to C₁₄, preferably Cm to C₁₄, and more preferentially C₁₂ to C₁₄ alkyl group.

According to a second embodiment, the group R₂ of formula (I) is a linear or branched C₁₄ to C₂₄, preferably C₁₆ to C₂₂, more preferentially C₁₈ to C₂₂ acyclic alkyl radical.

According to a particularly preferred embodiment, the group X is a group —CO—O—, X being linked to the vinyl carbon by the carbon atom, and the group R₂ is a linear or branched C₁₄ to C₂₄, preferably C₁₆ to C₂₂, more preferentially C₁₈ to C₂₂ acyclic alkyl radical.

The units according to this embodiment correspond to those derived from monomers selected from alkyl acrylates and methacrylates having a C₁₄ to C₂₄, preferably C₁₆ to C₂₂, and more preferentially C₁₈ to C₂₂ alkyl group.

The copolymer used in the present invention also comprises at least one unit of the following formula (II):

wherein

R is a substituted or unsubstituted imidazole ring.

The substituent(s) optionally present on the imidazole ring(s) can be saturated or unsaturated, and be particularly selected from hydrocarbon, oxygenated, nitrogenous, halogenated, etc. substituents.

According to an embodiment, the units of formula (II) are derived from one or more vinyl monomers bearing a group R as described above.

Mention can be made by way of particularly preferred example of 1-vinylimidazole (or N-vinylimidazole):

The copolymer used in the present invention can be optionally cross-linked. Preferably, it is not cross-linked.

The copolymer used in the present invention can be advantageously a random copolymer, or a block copolymer. According to a particularly preferred embodiment, it is a random copolymer.

The copolymer according to the invention contains advantageously from 50 to 99% in moles of units of formula (I), preferably from 60 to 95% in moles, more preferentially from 70 to 90% in moles, and more preferably from 75 to 90% in moles.

The copolymer according to the invention contains advantageously from 1 to 50% in moles of units of formula (II), preferably from 5 to 40% in moles, more preferentially from 10 to 30% in moles, and more preferably from 10 to 25% in moles.

Preferably, the copolymer used in the present invention only contains units of formula (I) and units of formula (II).

The copolymer used in the present invention can be obtained by copolymerising:

at least one monomer complying with the following formula (IA):

-   -   wherein     -   R₁, X and R₂ are as defined above, the preferred variants of R₁,         X and R₂ according to formula (I) described above also being         preferred variants of formula (IA), and

at least one monomer complying with the following formula (IIA):

-   -   wherein R is as defined above, the preferred variants of R         according to formula (II) described above also being preferred         variants of formula (IIA)

When the group X of the monomer of formula (IA) is the group —O—CO—, it being understood that the group —O—CO— is linked to the vinyl carbon by the oxygen atom, the monomer of formula (IA) is, preferably, selected from alkyl vinyl esters having a C₆ to C₂₄ alkyl group, and more preferentially from alkyl vinyl esters having a C₁₂ to C₁₄ or C₁₈ to C₂₂ alkyl group. The alkyl radical of the alkyl vinyl ester is linear or branched, cyclic or acyclic, preferably acyclic.

Of the alkyl vinyl ester monomers, mention can be made by way of non-restrictive example of vinyl octanoate, vinyl decanoate, vinyl dodecanoate, vinyl tetradecanoate, vinyl 2-ethylhexanoate.

When the group X of the monomer of formula (IA) is the group —CO—O—, it being understood that the group —CO—O— is linked to the vinyl carbon by the carbon atom, the monomer or formula (IA) is typically selected from alkyl acrylates and methacrylates having a C₆ to C₂₄ alkyl group, and more preferentially from alkyl acrylates and methacrylates having a C₁₂ to C₁₄ or C₁₈ to C₂₂ alkyl group.

Of the alkyl (meth)acrylates capable of being used as monomers in the manufacture of the copolymer of the invention, mention can be made of C₆ to C₂₄ alkyl acrylates and C₆ to C₂₄ alkyl methacrylates, and particularly, by way of non-restrictive examples: n-octyl acrylate, n-octyl methacrylate, n-decyl acrylate, n-decyl methacrylate, n-dodecyl acrylate, n-dodecyl methacrylate, ethyl-2-hexyl acrylate, ethyl-2-hexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, isodecyl acrylate, isodecyl methacrylate, C₁₂ to C₁₄ alkyl acrylates and C₁₂ to C₁₄ alkyl methacrylates, C₁₈ to C₂₂ alkyl acrylates and C₁₈ to C₂₂ alkyl methacrylates. Using C₁₂ to C₁₄ alkyl acrylates and C₁₂ to C₁₄ alkyl methacrylates is particularly preferred.

The monomers of formula (IIA) are vinyl monomers bearing a group R as described above.

Mention can be made by way of particularly preferred monomer of formula (IIA) of 1-vinylimidazole (or N-vinylimidazole) of formula:

It is understood that it would not be outside the scope of the invention if the polymer according to the invention were obtained from different monomers from those of formula (IA) and (IIA) above, insofar as the final copolymer corresponds to a polymer comprising units of formula (I) and units of formula (II) as defined above. For example, it would not be outside the scope of the invention, if the polymer were obtained by polymerising different monomers, followed by post-functionalisation. For example, the units of formula (I) can be obtained using acrylic acid, by a transesterification reaction.

The polymer according to the invention can be prepared according to any known polymerisation method. The different polymerisation and cross-linking techniques and conditions are described extensively in the literature and are part of the general knowledge of a person skilled in the art.

In the case of a random copolymer, conventional radical polymerisation can particularly be performed: the procedure generally involves mixing the different monomers in a suitable solvent, and the copolymerisation is initiated by means of a radical polymerisation agent.

In the case of a block copolymer, the procedure can particularly involve sequenced and controlled polymerisation. Such a polymerisation is, advantageously, selected from controlled radical polymerisation; for example, by Atom Transfer Radical Polymerisation (ATRP); Nitroxide-mediated polymerisation (NMP); degenerative transfer processes such as iodine transfer radical polymerisation (ITRP) or Reversible Addition-Fragmentation Chain Transfer (RAFT); ATRP-derived polymerisations such as polymerisations using initiators for continuous activator regeneration (ICAR) or using activators regenerated by electron transfer (ARGET).

The copolymer according to the invention has, advantageously, a weight average molar mass (Mw) between 1000 and 50,000 g·mol⁻¹, more preferentially between 1000 and 20,000, even more preferentially between 3,000 and 15,000 g·mol⁻¹.

The copolymer according to the invention has, advantageously, a number average molar mass (Mn) between 1000 and 50,000 g·mol⁻¹, more preferentially between 1000 and 20,000, even more preferentially between 2,000 and 10,000 g·mol⁻¹.

The number and weight average molar masses are measured by Size Exclusion Chromatography (SEC).

Use:

The copolymer described above is used to improve the cold-resistance properties of a fuel or combustible composition, in particular, of a composition selected from diesel fuels, biodiesels, B_(x) type fuel oils, fuel oils, preferably, heating oils.

The fuel or combustible composition is as described hereinafter and advantageously comprises at least one hydrocarbon cut obtained from one or more sources selected from the group consisting of mineral, preferably petroleum, animal, plant and synthetic sources.

Advantageously, said copolymer is used to improve the flow properties at low temperatures of the fuel or combustible during the storage and/or use thereof, at low temperatures, by lowering the cold filter plugging point (or CFPP, measured as per the standard NF EN 116) thereof and/or the pour point (or PP, measured as per the standard ASTM D 7346) and/or by delaying or preventing the settling of crystals, and preferably by lowering the cold filter plugging point (CFPP, measured as per the standard NF EN 116) thereof.

The copolymer according to the invention can be used to delay or prevent the settling of crystals of paraffins and more specifically of n-alkanes, preferably, n-alkanes containing at least 12 carbon atoms, more preferentially at least 20 carbon atoms, even more preferentially preferably at least 24.

According to a preferred embodiment, the copolymer according to the invention is used as a CFPP booster additive, i.e. in combination with a flow improvement additive or cold flow improver additive (or CFI).

The cold flow improver additive (CFI) is, preferably, selected from copolymers and terpolymers of ethylene and vinyl and/or acrylic ester(s), alone or in a mixture.

In this embodiment, the copolymer according to the invention is used to amplify the fluidifying effect of the cold flow improver additive, particularly by lowering the cold filter plugging point (CFPP) thereof and/or the pour point, and/or by delaying or preventing the settling of crystals, such as those containing paraffins.

This effect is usually known as a “CFPP booster” effect insofar as the presence of the copolymer according to the invention improves the fluidifying property of the CFI additive. This improvement results, in particular, in a significant reduction in the CFPP of the fuel or combustible composition to which this association has been added compared to the same fuel or combustible composition to which only the CFI additive has been added, at the same treatment rate. Generally, a significant reduction in the CFPP results in a decrease of at least 3° C. of the CFPP as per the standard NF EN 116.

According to a particularly preferred embodiment, the copolymer is used to amplify the fluidifying (flow) effect of the cold flow improver additive (CFI) by improving the Cold Filter Plugging Point (CFPP) of the fuel or combustible, the CFPP being measured as per the standard NF EN 116.

The copolymer can be added to the fuels or combustibles in the refinery, and/or be incorporated downstream from the refinery, optionally, in a mixture with other additives, in the form of an additive concentrate, also known as “additive package”.

The copolymer is advantageously used in the fuel or combustible at a content of at least 0.0001% by weight, with respect to the total weight of the fuel or combustible composition.

Preferably, the content of said copolymer ranges from 0.0001 to 0.01% by weight, preferably from 0.0002 to 0.005% by weight, and more preferably from 0.0003 to 0.003% by weight, with respect to the total weight of the fuel or combustible composition.

Additive Composition:

The invention also relates to an additive composition comprising a copolymer as described above, and one or more cold-resistance additive(s) different from the copolymer comprising units of formula (I) and units of formula (II) as described above.

According to a preferred embodiment, the cold-resistance additive(s) are selected from cold flow improver additives, paraffin anti-settling additives and/or dispersants, and mixtures of these additives.

The cold flow improver additives (CFI) can particularly be selected from copolymers and terpolymers of ethylene and vinyl and/or acrylic ester(s), alone or in a mixture. By way of example, mention can be made of ethylene and unsaturated ester copolymers, such as the ethylene/vinyl acetate (EVA), ethylene/vinyl propionate (EVP), ethylene/vinyl ethanoate (EVE), ethylene/methyl methacrylate (EMMA), and ethylene/alkyl fumarate copolymers described, for example, in the documents U.S. Pat. Nos. 3,048,479, 3,627,838, 3,790,359, 3,961,961 and EP261957. Mention can also be made of terpolymers or ethylene, vinyl acetate and another vinyl ester, for example vinyl neodecanoate.

According to a preferred embodiment, the composition contains at least one cold flow improver additive (CFI) selected from the copolymers of ethylene and vinyl ester(s), alone or in a mixture, in particular ethylene/vinyl acetate (EVA) copolymers, ethylene/vinyl propionate (EVP) copolymers and terpolymers of ethylene, vinyl acetate and another vinyl ester; more preferentially ethylene/vinyl acetate (EVA) copolymers and mixtures thereof with a terpolymer of ethylene, vinyl acetate and another vinyl ester, such as in particular vinyl neodecanoate.

In this embodiment, the weight ratio between the copolymer content according to the invention, on one hand, and the ethyl and vinyl ester copolymer content, on the other, is advantageously within the range from 0.01:100 to 20:100, preferably from 0.1:100 to 10:100, and more preferably from 0.5:100 to 5:100. A particularly preferred weight ratio is 1:100±10%.

The paraffin anti-settling additives and/or dispersants (WASA) can be particularly, but not restrictively, selected from the group consisting of (meth)acrylic acid/alkyl (meth)acrylate copolymers amidified by a polyamine, polyamine alkenylsuccinimides, derivatives of phthalamic acid and double-chain fatty amine; optionally grafted alkylphenol resins. Examples of such additives are given in the following documents: EP261959, EP593331, EP674689, EP327423, EP512889, EP832172; US2005/0223631; U.S. Pat. No. 5,998,530; WO93/14178.

The particularly preferred paraffin anti-settling additives and/or dispersants (WASA) are selected from alkylphenol resins and alkylphenol resins grafted for example with functional groups such as polyamines.

The additive composition can also comprise one or more other additives routinely used in fuels or combustibles, different from the copolymer according to the invention and the cold-resistance additives described above.

The additive composition can, typically, comprise one or more other additives selected from detergents, anti-corrosion agents, dispersants, demulsifiers, biocides, reodorisers, cetane number improvers, friction modifiers, lubricity additives or oiliness additives, combustion-aid agents (catalytic combustion and soot promoters), anti-wear agents and/or conductivity modifying agents.

Of these additives, mention can particularly be made of:

a) cetane number improvers, particularly (but not restrictively) selected from alkyl nitrates, preferably 2-ethyl hexyl nitrate, aryl peroxides, preferably benzyl peroxide, and alkyl peroxides, preferably ter-butyl peroxide;

b) anti-foaming agents, particularly (but not restrictively) selected from polysiloxanes, oxyalkylated polysiloxanes, and fatty acid amides obtained from vegetable or animal oils. Examples of such additives are given in EP861882, EP663000, EP736590;

c) detergent and/or anti-corrosion additives, particularly (but not restrictively) selected from the group consisting of amines, succinimides, alkenylsuccinimides, polyalkylamines, polyalkyl polyamines, polyetheramines, quaternary ammonium salts and triazole derivatives; examples of such additives are given in the following documents: EP0938535, US2012/0010112 and WO2012/004300. Block copolymers formed from at least one polar unit and one nonpolar unit can advantageously be used, such as for example those described in the patent application FR 1761700 held by the Applicant;

d) lubricity additives or anti-wear agents, particularly (but not restrictively) selected from the group consisting of fatty acids and the ester or amide derivatives thereof, particularly glycerol monooleate, and mono- and polycyclic carboxylic acid derivatives. Examples of such additives are given in the following documents: EP680506, EP860494, WO98/04656, EP915944, FR2772783, FR2772784.

The additive composition can, advantageously, comprise from 0.1 to 50% by weight of copolymer as described above, with respect to the total weight of the additive composition.

The present invention also relates to an additive concentrate comprising an additive composition as described above, in a mixture with an organic liquid. The organic liquid is advantageously inert with respect to the constituents of the additive composition, and miscible with fuels or combustibles, particularly those derived from one or more sources selected from the group consisting of mineral sources, preferably petroleum, animal, plant, and synthetic.

The organic liquid is preferably selected from aromatic hydrocarbon solvents such as the solvent marketed under the name “SOLVESSO”, alcohols, ethers and other oxygenated compounds, and paraffinic solvents such as hexane, pentane or isoparaffins, alone or in a mixture.

Fuel or Combustible Composition:

The invention also relates to a fuel or combustible composition, comprising:

(1) at least one hydrocarbon cut derived from one or more sources selected from the group consisting of mineral, animal, plant and synthetic sources, and

(2) at least one copolymer as defined above.

The mineral sources are preferably petroleum.

The fuel or combustible composition according to the invention advantageously comprises said copolymer(s) at a content of at least 0.0001% by weight, with respect to the total weight of the fuel or combustible composition. Preferably, the copolymer content ranges from 0.0001 to 0.01% by weight, preferably from 0.0002 to 0.005% by weight, and more preferably from 0.0003 to 0.003% by weight, with respect to the total weight of the fuel or combustible composition.

According to a preferred embodiment, said composition further comprises at least one cold-resistance additive, selected from cold-flow additives (CFI) and paraffin anti-settling additives and/or dispersants (WASA), different from the copolymers according to the invention comprising units of formula (I) and units of formula (II). Such additives are advantageously selected from those described above.

In this embodiment, the composition advantageously contains at least 20 ppm, preferably at least 50 ppm, advantageously between 20 and 5000 ppm, more preferentially between 50 and 1000 ppm in total of cold-resistance additive(s).

The fuels or combustibles can be selected from liquid hydrocarbon fuels or combustibles, alone or in a mixture. The liquid hydrocarbon fuels or combustibles particularly comprise middle distillates of boiling point between 100 and 500° C. These distillates can for example be selected from distillates obtained by direct distillation of crude hydrocarbons, vacuum distillates, hydrotreated distillates, distillates obtained from catalytic cracking and/or hydrocracking of vacuum distillates, distillates resulting from ARDS (atmospheric residue desulphurisation) and/or visbreaking type conversion processes, distillates obtained from Fischer Tropsch cut valorisation, distillates resulting from the BTL (biomass to liquid) conversion of plant and/or animal biomass, taken alone or in combination, and/or biodiesels of animal and/or plant origin and/or vegetable and/or animal oils and/or oil esters.

The sulphur content of the fuels or combustibles is, preferably, less than 5000 ppm, preferably less than 500 ppm, and more preferentially less than 50 ppm, or even less than 10 ppm, and advantageously free from sulphur.

The fuel or combustible is, preferably, selected from diesel fuels, biodiesels, B_(x) type diesel fuels and fuel oils, preferably, heating oils.

The term B_(x) type diesel fuel for a Diesel engine (compression engine) denotes a diesel fuel which contains x % (v/v) of plant or animal esters (including used cooking oils) converted by a chemical process known as transesterification reacting this oil with an alcohol in order to obtain fatty acid esters (FAE). With methanol and ethanol, fatty acid methyl esters (FAME) and fatty acid ethyl esters (FAEE) are respectively obtained. The letter “B” followed by a number x ranging from 0 to 100, which indicates the percentage of FAE contained in the diesel fuel. Thus, a B99 contains 99% FAE and 1% middle distillates of fossil origin, B20, 20% FAE and 80% middle distillates of fossil origin, etc. Therefore, a distinction is made between B₀ type diesel fuels which do not contain oxygenated compounds, B_(x) type diesel fuels which contain x % (v/v) vegetable or animal oil or fatty acid esters, most often methyl esters (VOME or FAME). When the FAE is used alone in engines, the fuel is denoted using the term B100.

The fuel or combustible can also contain hydrogenated vegetable oils, known to a person skilled in the art as HVO (hydrogenated vegetable oil) or HDRD (hydrogenation-derived renewable diesel).

According to a specific development, the fuel or combustible is selected from diesel fuels, biodiesels and Bx type diesel fuels, hydrogenated vegetable oils (HVO), and mixtures thereof.

The fuel or combustible composition can also contain one or more additional additives, different from the copolymers and the cold-resistance additives described above. Such additives can be particularly selected from detergents, anti-corrosion agents, dispersants, demulsifiers, anti-foaming agents, biocides, reodorisers, cetane number improvers, friction modifiers, lubricity additives or oiliness additives, combustion-aid agents (catalytic combustion and soot promoters), anti-wear agents and/or conductivity modifying agents.

These additional additives can be generally present in a quantity ranging from 50 to 1000 ppm (each).

According to a further embodiment of the invention, a method for improving the cold-resistance properties of a fuel or combustible composition comprises the successive steps of:

a) determining the most suitable additive composition for the fuel or combustible composition to be treated as well as the treatment rate required to attain a given specification relative to the cold-resistance properties for the specific fuel or combustible composition, said additive composition comprising at least one copolymer according to the invention and, optionally, at least one cold-resistance additive, selected from cold flow improver additives and paraffin anti-settling additives and/or dispersants, different from the copolymers comprising units of formula (I) and units of formula (II);

b) treating the fuel or combustible composition with the quantity determined in step a) of said additive composition.

The method for improving cold-resistance properties is typically intended for a fuel or combustible composition as described above.

Step a) is carried out according to any known method and is part of the routine practice in the field of fuel or combustible additivation. This step involves defining a representative characteristic of the cold-resistance properties of the fuel or combustible, for example the low-temperature flow characteristics, setting the target value then determining the improvement which is required to attain the specification.

For example, a specification relative to cold resistance can be a European Extreme Cold specification defining, in particular, a maximum CFPP as per the standard NF EN 116. The determination of the quantity of additive composition to be added to the fuel or combustible composition to attain the specification will be carried out typically by comparing with the fuel or combustible composition without said additive composition.

The quantity of copolymer required to treat the fuel or combustible composition can vary according to the nature and origin of the fuel or combustible, in particular according to the content and nature of the paraffinic compounds contained therein. The nature and origin of the fuel or combustible can therefore also be a factor to be taken into account for step a).

The method for improving the cold-resistance properties can also comprise an additional step after step b) of verifying the target attained and/or adjusting the treatment rate with the additive composition.

The examples hereinafter are given by way of illustration of the invention, and cannot be interpreted in such a way as to restrict the scope thereof.

EXAMPLES Example 1: Synthesis of Various Polymers

Starting Compounds:

-   -   Monomer 1: C₁₂/C₁₄ alkyl acrylate (A12/14) (CAS 2156-97-0 and         21643-42-5)     -   Monomer 2: 1-vinylimidazole (NVI) (CAS 1072-63-5)     -   Initiator: 2,2′-Azobis-(2-methylpropionitrile) (AIBN) (CAS         78-67-1)     -   Transfer agent: Butanethiol (CAS 109-79-5)     -   Control agent: Trithiocarbonate (CAS 558484-21-2)     -   Solvent: 1,4-Dioxane (CAS 123-91-1)

Synthesis Protocol of a C₁₂/C₁₄ Alkyl Acrylate and N-Vinylimidazole Random Copolymer with a Molar Ratio 80:20:

8.84 g (35.4 mmol) of C₁₂/C₁₄ alkyl acrylate, 0.832 g (8.84 mmol) of 1-vinylimidazole, 0.146 g (1.62 mmol) of butanethiol and 15.23 g (14.7 mL) of 1,4-Dioxane are introduced into a 25 mL round-bottom flask equipped with a nitrogen inlet and outlet. The mixture is then stirred and degassed with a nitrogen stream for 30 minutes. In parallel, a solution of AIBN (0.097 g; 0.57 mmol) in 1,4-Dioxane (1 mL) is also prepared and placed under degassing for 30 minutes. The round-bottom flask containing the reaction medium is placed under heating and once the target temperature has been attained (70° C.), the initiator solution is introduced to start the polymerisation. The reaction is left for 6 h at 70° C. At the end of the reaction, the heating is switched off and the medium is exposed to air to stop the polymerisation. The solvent is then evaporated in a vacuum to retrieve the polymer.

The random polymers of the different examples for which the characteristics are featured in table I hereinafter were synthesised according to this protocol. The quantity and nature of the monomers were adapted in each case.

Synthesis Protocol of a C₁₂/C₁₄ Alkyl Acrylate and N-Vinylimidazole Block Copolymer with a Molar Ratio 80:20

Synthesis of Block 1:

8.5 g (34 mmol) of C₁₂/C₁₄ alkyl acrylate, 0.329 g (0.94 mmol) of trithiocarbonate and 9.0 g of 1,4-Dioxane are introduced into a 25 mL round-bottom flask equipped with a nitrogen inlet and outlet. The mixture is then stirred and degassed with a nitrogen stream for 30 minutes. In parallel, a solution of AIBN (0.015 g; 0.094 mmol) in 1,4-Dioxane (1 mL) is also prepared and placed under degassing for 30 minutes. The round-bottom flask containing the reaction medium is placed under heating and once the target temperature has been attained (70° C.), the initiator solution is introduced to start the polymerisation. The reaction is left at 70° C. until the conversion into C₁₂/C₁₄ alkyl acrylate is greater than 95%.

Synthesis of Block 2:

0.795 g (8.46 mmol) of 1-vinylimidazole is introduced into the reaction medium obtained from the synthesis of block 1, and the mixture is stirred and degassed with a nitrogen stream for 30 minutes. In parallel, a new solution of AIBN (0.015 g; 0.094 mmol) is prepared in 1,4-Dioxane and placed under degassing for 30 minutes. The AIBN solution is then added to the reaction medium to restart the polymerisation. The reaction is left for 6 h at 70° C. At the end of the reaction, the heating is switched off and the medium is exposed to air to stop the polymerisation. The solvent is then evaporated in a vacuum to retrieve the polymer.

The block copolymers of the different examples for which the characteristics are featured in table I hereinafter were synthesised according to this protocol. The quantity of the monomers was adapted in each case.

The polymers were characterised by size exclusion chromatography (SEC), in order to determine the composition and molar mass of each copolymer.

The characteristics of the polymers synthetised according to the protocols described hereinabove are compiled in table I below:

M_(W) M_(n) Type of Monomer Monomer (g · (g · polymer of formula (I) of formula (II) mol⁻¹) mol⁻¹) Homopolymer C₁₂/C₁₄ alkyl — 7750 4920 acrylate Random C₁₂/C₁₄ alkyl N-vinylimidazole 8100 5700 copolymer acrylate 20% in moles 80% in moles Random c C₁₂/C₁₄ alkyl N-vinylimidazole 10230 6220 copolymer acrylate 10% in moles 90% in moles Random C₁₈/C₂₂ alkyl N-vinylimidazole 5900 3400 copolymer acrylate 20% in moles 80% in moles Block C₁₂/C₁₄ alkyl N-vinylimidazole 8613 7245 copolymer acrylate 20% in moles 80% in moles Block C₁₂/C₁₄ alkyl N-vinylimidazole 9559 7586 copolymer acrylate 10% in moles 90% in moles

Example 2: Evaluation of Cold-Resistance Performances

The polymers described in example 1 were tested as cold-resistance additives in a particularly difficult to treat diesel fuel type fuel composition G, and the characteristics of which are detailed in table II below:

Characteristic Method Value Density at 15° C. ISO 12185 831.2 kg/m³ Viscosity at 20° C. ISO 3104 5.1 mm²/s Viscosity at 40° C. ISO 3104 3.5 mm²/s Cloud point (CP) ° EN 23015 −3° C. Cold filter plugging EN 116 −2° C. point (CFPP) Pour point (PP) ASTM D 7346 −12° C. Paraffin content 21.42% by weight C16+ n-paraffin content 11.30% by weight D86 distillation point ISO 3405 Starting point 173.0° C. Point at 5% vol. 196.6° C. Point at 10% vol. 215.4° C. Point at 20% vol. 243.4° C. Point at 30% vol. 261.9° C. Point at 40% vol. 276.0° C. Point at 50% vol. 287.7° C. Point at 60% vol. 299.3° C. Point at 70% vol. 311.4° C. Point at 80% vol. 325.5° C. Point at 90% vol. 343.7° C. Point at 95% vol. 356.2° C. End point 359.0° C. Distilled volume 97.4 ml Residue 0.6 ml Losses 1.8 ml

A package containing the following two conventional commercial cold flow improver additives (CFI additives), in Solvesso 150 solvent, was added to the diesel fuel composition G:

-   -   0.5% by weight of CP7956C additive marketed by the company Total         Additifs Carburants S{acute over (p)}eciaux, and which is an         ethylene/vinyl acetate (EVA) copolymer;     -   0.5% by weight of Dodiflow D4134 additive marketed by the         company Clariant, and which is an ethylene/vinyl acetate/vinyl         neodecanoate terpolymer.

This package was incorporated in the diesel fuel composition G at a content of 300 ppm by weight of active substance (i.e. 150 ppm by weight of each additive) with respect to the total weight of the diesel fuel composition.

The additive-containing diesel fuel composition G1 was thus obtained. It has a Cold filter plugging point (CFPP, standard EN 116) of −6° C.

The performances as cold-resistance additives of each of the polymers of example 1 were tested, by evaluating their ability to lower the cold filter plugging point (CFPP) of the additive-containing diesel fuel composition G1.

Each polymer was added at a content of 3 ppm by weight (0.0003% by weight) to the composition G1, to produce the diesel fuel G2, the CFPP of which was then measured, in accordance with the standard EN 116.

The results obtained are featured in table III below:

CFPP (° C.) Difference in CFPP: Type of polymer Diesel fuel G2 CFPP G1 − CFPP G2 Homopolymer  −7° C. 1° C. C₁₂/C₁₄ alkyl acrylate Random copolymer −13° C. 7° C. C₁₂/C₁₄ alkyl acrylate/ N-vinylimidazole (80/20) Random copolymer −13° C. 7° C. C₁₂/C₁₄ alkyl acrylate/ N-vinylimidazole (90/10) Random copolymer −15° C. 9° C. C₁₈/C₂₂ alkyl acrylate/ N-vinylimidazole (80/20) Block copolymer −11° C. 5° C. C₁₂/C₁₄ alkyl acrylate/ N-vinylimidazole (80/20) Block copolymer −12° C. 6° C. C₁₈/C₂₂ alkyl acrylate/ N-vinylimidazole (90/10)

The above results show that using the copolymers according to the invention results in a significant lowering of the CFPP, ranging from 7 to 9 points for random copolymers, and from 5 to 6 points for block copolymers. 

1. A use, for improving the cold-resistance properties of a fuel or combustible composition, of one or more copolymers comprising: at least one unit of the following formula (I):

wherein R₁ is a hydrogen atom or a methyl group, X is —O—CO—, or —CO—O— or —NH—CO— or —CO—NH—, and R₂ is a C₆ to C₂₄ alkyl group; and at least one unit of the following formula (II):

wherein R is a substituted or unsubstituted imidazole ring.
 2. The use according to claim 1, characterised in that the group X of formula (I) is selected from: —CO—O— and —CO—NH—, it being understood that the group X is linked to the vinyl carbon by the carbon atom, and preferably the group X of formula (I) is the group —CO—O—.
 3. The use according to claim 1, characterised in that the group R2 of formula (I) is a linear or branched C₈ to C₂₄, preferably C₈ to C₁₄ or C₁₆ to C₂₂, more preferentially C₁₂ to C₁₄ or C₁₈ to C₂₂ and more preferably C₁₈ to C₂₂ acyclic alkyl radical.
 4. The use according to claim 1, characterised in that the unit of formula (II) is N-vinylimidazole.
 5. The use according to claim 1, characterised in that said copolymer contains from 1 to 50% in moles of units of formula (II), preferably from 5 to 40% in moles, more preferentially from 10 to 30% in moles, and more preferably from 10 to 25% in moles.
 6. The use according to claim 1, characterised in that said copolymer contains only units of formula (I) and units of formula (II).
 7. The use according to claim 1, characterised in that said copolymer is a random copolymer, or a block copolymer, and preferably said copolymer is a random copolymer.
 8. The use of a copolymer according to claim 1, for lowering the cold filter plugging point measured as per the standard NF EN 116 and/or the pour point measured as per the standard ASTM D 7346, and/or for delaying or preventing the settling of crystals, and preferably for lowering the cold filter plugging point measured as per the standard NF EN
 116. 9. The use according to claim 1, characterised in that said copolymer is used in combination with at least one cold flow improver additive, preferably selected from copolymers and terpolymers of ethylene and vinyl and/or acrylic ester(s), alone or in a mixture.
 10. An additive composition comprising a copolymer as defined in claim 1, and one or more cold-resistance additive(s) different from the copolymers comprising units of formula (I) and units of formula (II), preferably selected from cold flow improver additives, paraffin anti-settling additives and/or dispersants, and mixtures of these additives.
 11. The additive composition according to claim 10, characterised in that it contains at least one cold flow improver additive selected from the copolymers of ethylene and vinyl ester(s), alone or in a mixture; preferably selected from ethylene/vinyl acetate (EVA) copolymers, ethylene/vinyl propionate (EVP) copolymers and terpolymers of ethylene, vinyl acetate and another vinyl ester; more preferentially selected from ethylene/vinyl acetate (EVA) copolymers and mixtures thereof with a terpolymer of ethylene, vinyl acetate and another vinyl ester, such as vinyl neodecanoate in particular.
 12. The additive composition according to claim 1, characterised in that the weight ratio between the content of the copolymer(s) according to the invention, on one hand, and the content of copolymer(s) of ethylene and vinyl ester(s), on the other, is within the range from 0.01:100 to 20:100, preferably from 0.1:100 to 10:100, and more preferably from 0.5:100 to 5:100.
 13. A fuel or combustible composition, comprising: (1) at least one hydrocarbon cut derived from one or more sources selected from the group consisting of mineral, animal, plant and synthetic sources, and (2) at least one copolymer as defined in claim
 1. 14. The composition according to claim 13, characterised in that it contains said copolymer(s) at a content of at least 0.0001% by weight, preferably at a content ranging from 0.0001 to 0.01% by weight, preferably from 0.0002 to 0.005% by weight, and more preferably from 0.0003 to 0.003% by weight, with respect to the total weight of the composition.
 15. The composition according to claim 13, characterised in that it further comprises at least one cold flow improver additive selected from the copolymers of ethylene and vinyl ester(s), alone or in a mixture.
 16. The composition according to claim 14, characterised in that it further comprises at least one cold flow improver additive selected from ethylene/vinyl acetate (EVA) copolymers, ethylene/vinyl propionate (EVP) copolymers and terpolymers of ethylene, vinyl acetate and another vinyl ester; more preferentially selected from ethylene/vinyl acetate (EVA) copolymers and mixtures thereof with a terpolymer of ethylene, vinyl acetate and another vinyl ester, such as vinyl neodecanoate in particular. 